Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.77	6.683%	$186.4499	$186.45	$186.45	$186.40
Purchase #2	$240.74	6.117%	$255.4661	$255.47	$255.45	$255.50
Purchase #3	$79.86	6.464%	$85.0222	$85.02	$85.00	$85.00
Purchase #4	$27.60	8.164%	$29.8533	$29.85	$29.85	$29.90
Purchase #5	$250.73	5.468%	$264.4399	$264.44	$264.45	$264.40
Purchase #6	$83.78	13.606%	$95.1791	$95.18	$95.20	$95.20
Purchase #7	$168.78	6.239%	$179.3102	$179.31	$179.30	$179.30
7 purchase totals =	$1,026.26		$1,095.7207	$1,095.72	$1,095.70	$1,095.70